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Module 1: Evolution Month Day Topic Aug Sept 28 History of life on Earth 30 Timeline construction 1 Theory of evolution 4 Holiday 6 Evidence for evolution 8 Mechanisms of evolution I 11 Mechanisms of evolution II 13 Speciation Why did the chicken cross the road? Evolutionist 1: It was the logical next step after coming down from the trees. Evolutionist 2: The fittest chickens cross the road. Evolutionist 3: Pure chance. Creationist: God created the chicken on the other side of the road. There is no proof it ever was on this side. Misconceptions 1. Evolution is a theory about the origin of life. 2. Evolution is like a climb up a ladder of progress: organisms just keep getting better. 3. Evolution means that life changed “by chance.” 4. Natural selection involves organisms “trying” to adapt. 5. Evolution is just a “theory” 6. Evolution is a theory in crisis and is collapsing as scientists loose confidence in it Misconceptions 7. Gaps in the fossil record disprove evolution 8. Evolutionary theory is incomplete and is currently unable to give a total explanation of the changes in life 9. The theory of evolution is flawed, but scientists won’t admit it 10. Most biologists have rejected “Darwinism.” 11. Evolution is not science because it is not observable or testable Evolution has one implication: it explains the history of life Incorrect Implications 1. Evolution leads to immoral behavior 2. Evolution supports the idea of “might makes right” and rationalizes the oppression of some people by others 3. Evolution and religion are incompatible Evidence for evolution 1. 2. 3. 4. 5. Fossils Biogeography Morphology Development Biochemistry 1. Fossil evidence • Recognizable evidence of ancient life • 17th century, association of shark’s teeth and “tongue stones” • Hard body parts, tracks, feces Fossilization How do we know their age? Relative age: layering of rocks Geologic Time Scale • Boundaries based on transitions in fossil record Phanerozoic eon Cenozoic era Quaternary period Mesozoic era Cretaceous period Tertiary period Jurassic period Triassic period Paleozoic era Permian period Carboniferous period Devonian period Silurian period Ordovician period Cambrian Cambrianperiod period Proterozoic eon Figure 19.4 (2) Page 308 Archean eon and earlier How do we know their age? Absolute age: radiometric dating Uranium 238—half-life of 4.5 billion years Carbon 14—half-life of 5370 years Radiometric Dating parent isotope in newly formed rock after one half-lives after two half-lives Figure 19.5 Page 309 Geologic Time Scale • Boundaries based on transitions in fossil record MYA Phanerozoic eon Cenozoic era Mesozoic era Quaternary period 1 Tertiary period 65 Cretaceous period 138 Jurassic period Triassic period Paleozoic era 205 210 Permian period 290 Carboniferous period 370 Devonian period Silurian period Ordovician period Cambrian Cambrianperiod period 410 435 505 570 Proterozoic eon Figure 19.4 (2) Page 308 Archean eon and earlier 2,500 mya What does the fossil record tell us? • Lineages change over time • Intermediate forms exist • Most recent fossils look the most like modern life Why is it incomplete? • Few organisms get buried without getting eaten or decomposed • Few fossils avoid erosion, lava, and other geological events • Few organisms live in “preservation environments” • Many organisms do not have hard parts • Many fossil bearing strata have not been exposed 2. Biogeographic evidence • Continents were once joined and have since “drifted” apart • Initially based on the shapes and sutures of land masses • Mechanism: plate tectonics Changing Land Masses 420 mya 260 mya 65 mya 10 mya Figure 19.8c Page 311 2. Biogeographic evidence • Patterns of diversity explained by continental position • Continents that have been separated longest have the most divergent floras and faunas • Examples: marsupials in Australia, tropical and desert plants in South America… 3. Morphological evidence • Homologous structures • Guiding principle: –When it comes to introducing change in morphology, evolution tends to follow the path of least resistance Morphological Divergence 4 5 21 3 • Change from body form of a common ancestor 4 pterosaur 1 chicken 2 3 1 2 bat 3 4 • Produces homologous structures Figure 19.10 Page 312 3 early reptile 21 1 5 porpoise 2 4 3 5 penguin 2 1 2 3 4 5 3 human 4. Developmental evidence • Each animal or plant proceeds through a series of changes in form • Similarities in these stages may be clues to evolutionary relationships • Mutations that disrupt a key stage of development are selected against Altering Developmental Programs • Some mutations shift a step in a way that natural selection favors • Small changes at key steps may bring about major differences • Insertion of transposons or gene mutations Similar Vertebrate Embryos • Alterations that disrupted early development have been selected against FISH REPTILE BIRD MAMMAL Figure 19.13a Page 315 Developmental Changes • Changes in the onset, rate, or time of completion of development steps can cause changes in form • Ex: Adult forms that retain juvenile features Proportional Changes in Skull Chimpanzee Human Figure 19.14b Page 315 5. Biochemical evidence • Kinds and numbers of biochemical traits that species share is a clue to how closely they are related • Can compare DNA, RNA, or proteins • More similarity means species are more closely related Comparing Proteins • Compare amino acid sequence of proteins produced by the same gene • Human cytochrome c (a protein) –Identical amino acids in chimpanzee protein –Chicken protein differs by 18 amino acids –Yeast protein differs by 56 Sequence Conservation • Cytochrome c functions in electron transport • Deficits in this vital protein would be lethal • Long sequences are identical in wheat, yeast, and a primate Sequence Conservation Yeast Wheat Primate Figure 19.15 Page 316-317